Polypropylene - carbon fiber composite

ABSTRACT

The present invention refers to a fiber reinforced polymer composition comprising a polypropylene, carbon fibers and a polar modified polypropylene as coupling agent as well as to an article comprising the fiber reinforced polymer composition.

The present invention refers to a fiber reinforced polymer composition comprising a polypropylene, carbon fibers and a polar modified polypropylene as coupling agent as well as to an article comprising the fiber reinforced polymer composition.

The requirements in terms of mechanical performances of polypropylenes are getting more and more demanding. It is especially desirable achieving a well-balanced property profile with regard to stiffness and impact. Polymer design and modality are a great tool to modify material properties, but there are certain intrinsic physical limitations in this regard. In particular, thickness reduction has become a very common method for reducing the weight of parts. However, by doing so the stiffness of the used material must be increased for compensating the smaller cross-section. Thus, fillers such as talc and glass fibers are typically incorporated in the polypropylene matrix, which allow the obtained reinforced material to achieve the desired mechanical properties. However, said fillers have a relatively high density and thus again increase the overall density of the polypropylene.

Accordingly, the industries seek for a fiber-reinforced composition fulfilling the demanding requirements of increasing the stiffness of a polypropylene and reducing the density of the fiber-reinforced composition compared to glass fibre filled materials. It is also desired to improve the impact related properties of the fiber-reinforced composition.

The finding of the present invention is to use a fiber reinforced polymer composition comprising carbon fibers in combination with a specific polar modified polypropylene in a polypropylene matrix.

Accordingly the present invention is directed to a fiber reinforced polymer composition comprising

-   (a) from 39 to 94 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polypropylene (PP); -   (b) from 5 to 60 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of carbon fibers (CF); and -   (c) from 1 to 10 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polar modified polypropylene     (PMP) as coupling agent, wherein the polar modified polypropylene     (PMP) comprises groups derived from polar groups in an amount of     from 1 to 5 wt.-%, like from 1.0 to 5.0 wt.-%, based on the total     weight of the polar modified polypropylene (PMP),

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

In one embodiment, the polypropylene (PP) has

-   (a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to     ISO 1133 of not more than 75 g/10 min; and/or -   (b) a melting temperature T_(m) in the range of 160 to 170° C.

In another embodiment, the polypropylene (PP) is a propylene homopolymer (H-PP1) and/or a propylene copolymer (C-PP1), preferably a propylene homopolymer (H-PP1).

In one embodiment, the non-woven fabric comprises at least 50 wt.-% carbon fibers (CF), based on the total weight of the non-woven fabric.

In another embodiment, the carbon fibers (CF) comprise a sizing agent.

In yet another embodiment, the fiber reinforced polymer composition is free of fibers (F) being selected from the group comprising glass fibers, metal fibers, mineral fibers, ceramic fibers and mixtures thereof.

In one embodiment, the polar modified polypropylene (PMP) comprises groups derived from polar groups selected from the group consisting of acid anhydrides, carboxylic acids, carboxylic acid derivatives, primary and secondary amines, hydroxyl compounds, oxazoline and epoxides, and also ionic compounds.

In another embodiment, the polar modified polypropylene (PMP) is a propylene polymer grafted with maleic anhydride.

In yet another embodiment, the polar modified polypropylene (PMP) is a propylene copolymer grafted with maleic anhydride, preferably the propylene copolymer grafted with maleic anhydride comprises ethylene as comonomer units.

In one embodiment, the fiber reinforced polymer composition further comprises at least one additive in an amount of up to 20 wt.-%, based on the total weight of the fiber reinforced polymer composition.

In another embodiment, the fiber reinforced polymer composition further comprises 2 to 15 wt.-%, based on the total weight of the fiber reinforced polymer composition, of an elastomeric copolymer (ECP) comprising units derived from ethylene and C₄ to C₈ α-olefins.

In yet another embodiment, the fiber reinforced polymer composition has

-   (a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to     ISO 1133 of from 5 to 75 g/10 min; and/or -   (b) density of equal or less than 1.200 g/cm³; and/or -   (c) a Charpy notched impact strength at +23° C. of ≥5.5 kJ/m²;     and/or -   (d) a tensile strength according to ISO 527-2 of at least 100 MPa.

Another aspect of the present invention is directed to an article comprising the fiber reinforced polymer composition as defined herein. Preferably, the article is a molded article, more preferably an injection molded article or a foamed article. It is further preferred that the article is a part of washing machines or dishwashers or automotive articles, especially of car interiors and exteriors, like instrumental carriers, shrouds, structural carriers, bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like.

Where the term “comprising” is used in the present description and claims, it does not exclude other elements. For the purposes of the present invention, the term “consisting of” is considered to be a preferred embodiment of the term “comprising of”. If hereinafter a group is defined to comprise at least a certain number of embodiments, this is also to be understood to disclose a group, which preferably consists only of these embodiments.

Where an indefinite or definite article is used when referring to a singular noun, e.g. “a”, “an” or “the”, this includes a plural of that noun unless something else is specifically stated.

Terms like “obtainable” or “definable” and “obtained” or “defined” are used interchangeably. This e.g. means that, unless the context clearly dictates otherwise, the term “obtained” does not mean to indicate that e.g. an embodiment must be obtained by e.g. the sequence of steps following the term “obtained” even though such a limited understanding is always included by the terms “obtained” or “defined” as a preferred embodiment.

In the following the invention is defined in more detail.

The Fiber Reinforced Polymer Composition

The fiber reinforced polymer composition according to this invention comprises a polypropylene (PP), carbon fibers (CF), and a polar modified polypropylene (PMP) as coupling agent.

Accordingly, the fiber reinforced polymer composition comprises

-   (a) from 39 to 94 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polypropylene (PP); -   (b) from 5 to 60 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of carbon fibers (CF); and -   (c) from 1 to 10 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polar modified polypropylene     (PMP) as coupling agent, wherein the polar modified polypropylene     (PMP) comprises groups derived from polar groups in an amount of     from 1 to 5 wt.-%, like from 1.0 to 5.0 wt.-%, based on the total     weight of the polar modified polypropylene (PMP),

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

Additionally, the fiber reinforced polymer composition may comprise at least one additive.

Accordingly it is preferred that the fiber reinforced polymer composition comprises

-   (a) from 39 to 94 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polypropylene (PP); -   (b) from 5 to 60 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of carbon fibers (CF); -   (c) from 1 to 10 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polar modified polypropylene     (PMP) as coupling agent, wherein the polar modified polypropylene     (PMP) comprises groups derived from polar groups in an amount of     from 1 to 5 wt.-%, like from 1.0 to 5.0 wt.-%, based on the total     weight of the polar modified polypropylene (PMP); and -   (d) up to 20 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of at least one additive,

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

The fiber reinforced polymer composition may comprises an elastomeric copolymer (ECP) comprising units derived from ethylene and C₄ to C₈ α-olefins Accordingly it is preferred that the fiber reinforced polymer composition comprises

-   (a) from 39 to 94 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polypropylene (PP); -   (b) from 5 to 60 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of carbon fibers (CF); -   (c) from 1 to 10 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polar modified polypropylene     (PMP) as coupling agent, wherein the polar modified polypropylene     (PMP) comprises groups derived from polar groups in an amount of     from 1 to 5 wt.-%, like from 1.0 to 5.0 wt.-%, based on the total     weight of the polar modified polypropylene (PMP); and -   (d) from 2 to 15 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of an elastomeric copolymer (ECP)     comprising units derived from ethylene and C₄ to C₈ α-olefins,

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

Thus, it is especially preferred that the fiber reinforced polymer composition comprises, consists of,

-   (a) from 39 to 94 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polypropylene (PP); -   (b) from 5 to 60 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of carbon fibers (CF); -   (c) from 1 to 10 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polar modified polypropylene     (PMP) as coupling agent, wherein the polar modified polypropylene     (PMP) comprises groups derived from polar groups in an amount of     from 1 to 5 wt.-%, like from 1.0 to 5.0 wt.-%, based on the total     weight of the polar modified polypropylene (PMP); and -   (d) up to 20 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of at least one additive; and/or -   (e) from 2 to 15 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of an elastomeric copolymer (ECP)     comprising units derived from ethylene and C₄ to C₈ α-olefins,

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

For example, the fiber reinforced polymer composition comprises, preferably consists of,

-   (a) from 39 to 94 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polypropylene (PP); -   (b) from 5 to 60 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of carbon fibers (CF); -   (c) from 1 to 10 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polar modified polypropylene     (PMP) as coupling agent, wherein the polar modified polypropylene     (PMP) comprises groups derived from polar groups in an amount of     from 1 to 5 wt.-%, like from 1.0 to 5.0 wt.-%, based on the total     weight of the polar modified polypropylene (PMP); and -   (d) up to 20 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of at least one additive; or -   (e) from 2 to 15 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of an elastomeric copolymer (ECP)     comprising units derived from ethylene and C₄ to C₈ α-olefins,

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

Alternatively, the fiber reinforced polymer composition comprises, preferably consists of,

-   (a) from 39 to 94 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polypropylene (PP); -   (b) from 5 to 60 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of carbon fibers (CF); -   (c) from 1 to 10 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of a polar modified polypropylene     (PMP) as coupling agent, wherein the polar modified polypropylene     (PMP) comprises groups derived from polar groups in an amount of     from 1 to 5 wt.-%, like from 1.0 to 5.0 wt.-%, based on the total     weight of the polar modified polypropylene (PMP); -   (d) up to 20 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of at least one additive; and -   (e) from 2 to 15 wt.-%, based on the total weight of the fiber     reinforced polymer composition, of an elastomeric copolymer (ECP)     comprising units derived from ethylene and C₄ to C₈ α-olefins,

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

In one embodiment, the fiber reinforced polymer composition according to this invention does not comprise fibers (F) being selected from the group comprising glass fibers, metal fibers, mineral fibers, ceramic fibers and mixtures thereof. More preferably, the fiber reinforced polymer composition according to this invention does not comprise fibers (F) other than carbon fibers (CF).

In one embodiment, the fiber reinforced polymer composition according to this invention does not comprise (a) further polymer(s) different to the polymers present in the fiber reinforced polymer composition, i.e. different to the polypropylene (PP), the polar modified polypropylene (PMP) and the optional elastomeric copolymer (ECP) in an amount exceeding in total 10 wt.-%, preferably exceeding in total 5 wt.-%, based on the total weight of the fiber reinforced polymer composition. Typically if an additional polymer is present, such a polymer is a carrier polymer for additives and thus does not contribute to the improved properties of the claimed fiber reinforced polymer composition.

Accordingly in one specific embodiment the fiber reinforced polymer composition consists of the polypropylene (PP), the polar modified polypropylene (PMP), the carbon fibers (CF), the optional elastomeric copolymer (ECP) and the optional at least one additive, which might contain low amounts of polymeric carrier material. However this polymeric carrier material is not more than 10 wt.-%, preferably not more than 5 wt.-%, based on the total weight of the fiber reinforced polymer composition, present in said fiber reinforced polymer composition.

Therefore the present invention is especially directed to a fiber reinforced polymer composition comprising, preferably consists of,

-   (a) from 39 to 94 wt.-%, more preferably from 45 to 90 wt.-%, most     preferably from 55 to 80 wt.-%, like from 60 to 70 wt.-%, based on     the total weight of the fiber reinforced polymer composition, of a     polypropylene (PP); -   (b) from 5 to 60 wt.-%, more preferably from 10 to 50 wt.-%, most     preferably from 12.5 to 40 wt.-%, like from 15 to 25 wt.-%, based on     the total weight of the fiber reinforced polymer composition, of     carbon fibers (CF); and -   (c) from 1 to 10 wt.-%, more preferably from 2 to 8 wt.-%, most     preferably from 3 to 7 wt.-%, like from 4 to 6 wt.-%, based on the     total weight of the fiber reinforced polymer composition, of a polar     modified polypropylene (PMP) as coupling agent, wherein the polar     modified polypropylene (PMP) comprises groups derived from polar     groups in an amount of from 1 to 5 wt.-%, like from 1.0 to 5.0     wt.-%, based on the total weight of the polar modified polypropylene     (PMP),

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

For example, the present invention is directed to a fiber reinforced polymer composition comprising, preferably consists of,

-   (a) from 39 to 94 wt.-%, more preferably from 45 to 90 wt.-%, most     preferably from 55 to 80 wt.-%, like from 60 to 70 wt.-%, based on     the total weight of the fiber reinforced polymer composition, of a     polypropylene (PP); -   (b) from 5 to 60 wt.-%, more preferably from 10 to 50 wt.-%, most     preferably from 12.5 to 40 wt.-%, like from 15 to 25 wt.-%, based on     the total weight of the fiber reinforced polymer composition, of     carbon fibers (CF); -   (c) from 1 to 10 wt.-%, more preferably from 2 to 8 wt.-%, most     preferably from 3 to 7 wt.-%, like from 4 to 6 wt.-%, based on the     total weight of the fiber reinforced polymer composition, of a polar     modified polypropylene (PMP) as coupling agent, wherein the polar     modified polypropylene (PMP) comprises groups derived from polar     groups in an amount of from 1 to 5 wt.-%, like from 1.0 to 5.0     wt.-%, based on the total weight of the polar modified polypropylene     (PMP); and -   (d) up to 20 wt.-%, more preferably from 0.1 to 10 wt.-%, most     preferably from 0.1 to 5 wt.-%, like from 0.1 to 2 wt.-%, based on     the total weight of the fiber reinforced polymer composition, of at     least one additive; and/or -   (e) from 2 to 15 wt.-%, more preferably from 4 to 15 wt.-%, most     preferably from 6 to 13 wt.-%, like from 8 to 12 wt.-%, based on the     total weight of the fiber reinforced polymer composition, of an     elastomeric copolymer (ECP) comprising units derived from ethylene     and C₄ to C₈ α-olefins,

wherein preferably the carbon fibers (CF) are in the form of a non-woven fabric.

It is appreciated that the instant fiber-reinforced composition has exceptional mechanical properties such as increased stiffness and impact at low density, especially compared to glass fibre filled materials.

Thus, the fiber reinforced polymer composition preferably has

-   (a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to     ISO 1133 of from 5 to 75 g/10 min; and/or -   (b) density of equal or less than 1200 kg/m³; and/or -   (c) a Charpy notched impact strength at +23° C. of ≥5.5 kJ/m²;     and/or -   (d) a tensile strength according to ISO 527-2 of at least 100 MPa.

For example the fiber reinforced polymer composition has

-   (a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to     ISO 1133 of from 5 to 75 g/10 min, more preferably of from 5 to 50     g/10 min, most preferably of from 7.5 to 30 g/10 min, like from 10     to 15 g/10 min; or -   (b) density of equal or less than 1.200 g/cm³, more preferably in     the range of 0.800 to 1.200 g/cm³, most preferably in the range of     0.850 to 1.150 g/cm³, like in the range of 0.900 to 1.100 g/cm³; or -   (c) a Charpy notched impact strength at +23° C. of ≥5.5 kJ/m², more     preferably in the range of 5.5 to 18 kJ/m², most preferably in the     range of 6 to 15 kJ/m², like in the range of 6 to 10 kJ/m²; or -   (d) a tensile strength according to ISO 527-2 of at least 100 MPa,     more preferably in the range of 100 to 140 MPa, most preferably in     the range of 100 to 130, like in the range of 106 to 120 MPa.

Alternatively, the fiber reinforced polymer composition has

-   (a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to     ISO 1133 of from 5 to 75 g/10 min, more preferably of from 5 to 50     g/10 min, most preferably of from 7.5 to 30 g/10 min, like from 10     to 15 g/10 min; and -   (b) density of equal or less than 1.200 g/cm³, more preferably in     the range of 0.800 to 1.200 g/cm³, most preferably in the range of     0.850 to 1.150 g/cm³, like in the range of 0.900 to 1.100 g/cm³; and -   (c) a Charpy notched impact strength at +23° C. of ≥5.5 kJ/m², more     preferably in the range of 5.5 to 18 kJ/m², most preferably in the     range of 6 to 15 kJ/m², like in the range of 6 to 10 kJ/m²; and -   (d) a tensile strength according to ISO 527-2 of at least 100 MPa,     more preferably in the range of 100 to 140 MPa, most preferably in     the range of 100 to 130, like in the range of 106 to 120 MPa.

In addition, the present invention also relates to a process for the preparation of the fiber reinforced polymer composition as described above and in more detail below, comprising the steps of adding

-   (a) the polypropylene (PP); -   (b) the carbon fibers (CF); -   (c) the polar modified polypropylene (PMP); -   (d) the optional at least one additive; -   (e) the optional elastomeric copolymer (ECP) comprising units     derived from ethylene and C₄ to C₈ α-olefins; -   to an extruder and extruding the same obtaining said fiber     reinforced polymer composition.

The fiber reinforced polymer composition according to the invention may be compounded and pelletized using any of the variety of compounding and blending machines and methods well known and commonly used in the resin compounding art. However, it is preferred using a compounding and blending method that does not affect the carbon fiber dimensions.

For blending the individual components of the instant composition a conventional compounding or blending apparatus, e.g. a Banbury mixer, a 2-roll rubber mill, Buss-co-kneader or a twin screw extruder may be used. The polymer materials recovered from the extruder/mixer are usually in the form of pellets. These pellets are then preferably further processed, e.g. by injection molding to generate articles and products of the inventive composition.

In the following the individual components of the fiber reinforced polymer composition are described in more detail.

The Polypropylene (PP)

The fiber reinforced polymer composition must comprise a polymer component. To achieve the well-balanced mechanical properties such as high stiffness and impact at low density, the polymer must contain a specific polypropylene. Good density values can be inter alia achieved due to the presence of a polypropylene (PP). Preferably, a polypropylene (PP) having a high molecular weight.

In the present invention the term “polypropylene (PP)” encompasses propylene homopolymers and/or propylene copolymers.

Moreover, the term “propylene copolymer” encompasses propylene random copolymers, heterophasic polymers and mixtures thereof.

As known for the skilled person, random propylene copolymer is different from heterophasic polypropylene which is a propylene copolymer comprising a propylene homo or random copolymer matrix component (1) and an elastomeric copolymer component (2) of propylene with one or more of ethylene and C₄-C₈ alpha-olefin copolymers, wherein the elastomeric (amorphous) copolymer component (2) is dispersed in said propylene homo or random copolymer matrix polymer (1).

In one embodiment of the present invention, the polypropylene (PP) being present in the fiber reinforced polymer composition is a propylene homopolymer (H-PP1) and/or a propylene copolymer (C-PP1). For example, the fiber reinforced polymer composition comprises a propylene homopolymer (H-PP1) and a propylene copolymer (C-PP1). Alternatively, the fiber reinforced polymer composition comprises a propylene homopolymer (H-PP1) or a propylene copolymer (C-PP1).

In one specific embodiment, the fiber reinforced polymer composition comprises a propylene homopolymer (H-PP1) as the polypropylene (PP).

It is preferred that the polypropylene (PP) has a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to ISO 1133 of not more than 100 g/10 min, more preferably in the range of 2 to 50 g/10 min, still more preferably in the range of 5 to 30 g/10 min, like in the range of 10 to 25 g/10 min.

Additionally or alternatively, the polypropylene (PP) has a melting temperature T_(m) in the range of 160 to 170° C., like in the range of 162 to 170° C.

For example, the polypropylene (PP) has a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to ISO 1133 of not more than 100 g/10 min, more preferably in the range of 2 to 50 g/10 min, still more preferably in the range of 5 to 30 g/10 min, like in the range of 10 to 25 g/10 min, or a melting temperature T_(m) in the range of 160 to 170° C., like in the range of 162 to 170° C.

Preferably, the polypropylene (PP) has a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to ISO 1133 of not more than 100 g/10 min, more preferably in the range of 2 to 50 g/10 min, still more preferably in the range of 5 to 30 g/10 min, like in the range of 10 to 25 g/10 min, and a melting temperature T_(m) in the range of 160 to 170° C., like in the range of 162 to 170° C.

In the following the polypropylene (PP) being part of the fiber reinforced polymer composition will be defined in more detail.

In one embodiment, the fiber reinforced polymer composition comprises a propylene homopolymer (H-PP1).

The expression propylene homopolymer as used throughout the instant invention relates to a polypropylene that consists substantially, i.e. of more than 99.5 wt.-%, still more preferably of at least 99.7 wt.-%, like of at least 99.8 wt.-%, of propylene units. In a preferred embodiment only propylene units in the propylene homopolymer are detectable.

In a preferred embodiment, good stiffness is achieved due to the presence of a propylene homopolymer (H-PP1) with moderately high molecular weight. Accordingly it is preferred that the propylene homopolymer (H-PP1) has a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to ISO 1133 of not more than 100 g/10 min, more preferably in the range of 2 to 50 g/10 min, still more preferably in the range of 5 to 30 g/10 min, like in the range of 10 to 25 g/10 min.

Additionally or alternatively, the propylene homopolymer (H-PP1) has a melting temperature T_(m) in the range of 160 to 170° C., like in the range of 162 to 170° C.

Preferably, the propylene homopolymer (H-PP1) has a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to ISO 1133 of not more than 100 g/10 min, more preferably in the range of 2 to 50 g/10 min, still more preferably in the range of 5 to 30 g/10 min, like in the range of 10 to 25 g/10 min; and a melting temperature T_(m) in the range of 160 to 170° C., like in the range of 162 to 170° C.

The propylene homopolymer (H-PP1) preferably features a low amount of xylene cold solubles (XCS), i.e. of ≤4.0 wt.-%, preferably in the range from 0.1 to 4.0 wt.-%, more preferably in the range from 0.1 to 3.0 wt.-% and most preferably in the range from 0.1 to 2.5 wt.-%.

The propylene homopolymer (H-PP1) is preferably an isotactic propylene homopolymer. Accordingly, it is appreciated that the propylene homopolymer (H-PP1) has a rather high isotactic pentad concentration, i.e. higher than 90 mol-%, more preferably higher than 92 mol-%, still more preferably higher than 93 mol-% and yet more preferably higher than 95 mol-%, like higher than 97 mol-%.

The propylene homopolymer (H-PP1) is state of the art and commercially available. A suitable propylene homopolymer is for instance Bormed HF955MO of Borealis AG.

Additionally or alternatively, the polypropylene (PP) is a propylene copolymer (C-PP1).

The term “propylene copolymer (C-PP1)” covers random propylene copolymers (RC-PP1) as well as complex structures, like heterophasic systems.

The term “random propylene copolymer” denotes a copolymer of propylene monomer units and comonomer units, in which the comonomer units are randomly distributed in the polymeric chain. Thus, a random copolymer is different from a heterophasic copolymer comprising a matrix phase and an elastomeric phase dispersed therein, as described in detail below. Accordingly, the random propylene copolymer (RC-PP1) does not contain an elastomeric polymer phase dispersed therein, i.e. is monophasic and has just one glass transition temperature. However, the random propylene copolymer (RC-PP1) can be the matrix phase of a heterophasic propylene copolymer (HECO). The presence of second phases or the so called inclusions are for instance visible by high resolution microscopy, like electron microscopy or atomic force microscopy, or by dynamic mechanical thermal analysis (DMTA). Specifically in DMTA the presence of a multiphase structure can be identified by the presence of at least two distinct glass transition temperatures.

Thus, the random propylene copolymer (RC-PP1) preferably comprises, preferably consist of, units derived from

-   (i) propylene and -   (ii) ethylene and/or at least one C₄ to C₂₀ α-olefin, preferably at     least one α-olefin selected from the group consisting of ethylene,     1-butene, 1-pentene, 1-hexene and 1-octene, more preferably ethylene     and/or 1-butene, yet more preferably ethylene.

Accordingly, the random propylene copolymer (RC-PP1) may comprise units derived from propylene, ethylene and optionally at least another C₄ to C₁₀ α-olefin. In one embodiment of the present invention, the random propylene copolymer (RC-PP1) comprises units derived from propylene, ethylene and optionally at least another α-olefin selected from the group consisting of C₄ α-olefin, C₅ α-olefin, C₆ α-olefin, C₇ α-olefin, C₈ α-olefin, C₉ α-olefin and C₁₀ α-olefin. More preferably the random propylene copolymer (RC-PP1) comprises units derived from propylene, ethylene and optionally at least another α-olefin selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene, wherein 1-butene and 1-hexene are preferred. It is in particular preferred that the random propylene copolymer (RC-PP1) consists of units derived from propylene and ethylene. Preferably, the units derivable from propylene constitutes the main part of the propylene copolymer (C-PP1), i.e. at least 80 wt.-%, more preferably of at least 85 wt.-%, still more preferably of 80 to 99.5 wt.-%, yet more preferably of 85 to 99.5 wt.-%, still more preferably of 90 to 99.2 wt.-%, based on the total weight of the random propylene copolymer (RC-PP1). Accordingly, the amount of units derived from C₂ to C₂₀ α-olefins other than propylene in the random propylene copolymer (RC-PP1) is in the range of 0.5 to 20 wt.-%, more preferably of 0.5 to 15 wt.-%, still more preferably of 0.8 to 10 wt.-%, based on the total weight of the random propylene copolymer (RC-PP1). It is in particular appreciated that the amount of ethylene in the random propylene copolymer (RC-PP1), in particular in case the random propylene copolymer (RC-PP1) comprises only units derivable from propylene and ethylene, is in the range of 0.5 to 20 wt.-%, preferably of 0.8 to 15 wt.-%, more preferably of 0.8 to 10 wt.-%, based on the total weight of the random propylene copolymer (RC-PP1).

Additionally, it is appreciated that the random propylene copolymer (RC-PP1) has a melting temperature T_(m) of at least 130° C., preferably in the range of 130 to 160° C., more preferably in the range of 135 to 158° C., like in the range of 140 to 155° C.

Concerning the melt flow rate MFR₂ (230° C.), is appreciated that the random propylene copolymer (RC-PP1) preferably has a melt flow rate MFR₂ (230° C.) measured according to ISO 1133 of not more than 100 g/10 min, more preferably in the range of 2.0 to 50 g/10 min, still more preferably in the range of 5.0 to 30 g/10 min, like in the range of 8.0 to 25 g/10 min.

In one specific embodiment of the present invention, the polypropylene (PP) is a heterophasic propylene copolymer (HECO) or a mixture of a heterophasic propylene copolymer (HECO) and propylene homopolymer (H-PP1) and/or a random propylene copolymer (RC-PP1), more preferably the polypropylene (PP) is a heterophasic propylene copolymer (HECO) or a mixture of a heterophasic propylene copolymer (HECO) and propylene homopolymer (H-PP1).

Preferably the heterophasic propylene copolymer (HECO) comprises

-   a) a polypropylene matrix (M-HECO), and -   b) an elastomeric propylene copolymer (E).

The expression “heterophasic” indicates that the elastomeric copolymer (E) is preferably (finely) dispersed at least in the polypropylene matrix (M-HECO) of the heterophasic propylene copolymer (M-HECO). In other words the elastomeric copolymer (E) forms inclusions in the polypropylene matrix (M-HECO). Thus, the polypropylene matrix (M-HECO) contains (finely) dispersed inclusions being not part of the matrix and said inclusions contain the elastomeric copolymer (E). The term “inclusion” according to this invention shall preferably indicate that the matrix and the inclusion form different phases within the heterophasic propylene copolymer (M-HECO), said inclusions are for instance visible by high resolution microscopy, like electron microscopy or scanning force microscopy. Furthermore, the heterophasic propylene copolymer (HECO) preferably comprises as polymer components only the polypropylene matrix (M-HECO) and the elastomeric copolymer (E). In other words the heterophasic propylene copolymer (HECO) may contain further additives but no other polymer in an amount exceeding 5 wt-%, more preferably exceeding 3 wt.-%, like exceeding 1 wt.-%, based on the total heterophasic propylene copolymer (HECO), more preferably based on the polymers present in the heterophasic propylene copolymer (HECO). One additional polymer which may be present in such low amounts is a polyethylene which is a reaction product obtained by the preparation of the heterophasic propylene copolymer (HECO). Accordingly, it is in particular appreciated that a heterophasic propylene copolymer (HECO) as defined in the instant invention contains only a polypropylene matrix (M-HECO), an elastomeric copolymer (E) and optionally a polyethylene in amounts as mentioned in this paragraph.

The elastomeric copolymer (E) is preferably an elastomeric propylene copolymer (E1).

As explained above a heterophasic propylene copolymer (HECO) comprises a polypropylene matrix (M-HECO) in which the elastomeric copolymer (E), such as the elastomeric propylene copolymer (E1), is dispersed.

The polypropylene matrix (M-HECO) can be a propylene homopolymer (H-PP2) or a random propylene copolymer (RC-PP2).

However, it is preferred that the propylene matrix (M-HECO) is a propylene homopolymer (H-PP2).

The polypropylene matrix (M-HECO) being a propylene homopolymer (H-PP2) has a rather low xylene cold soluble (XCS) content, i.e. of not more than 3.5 wt.-%, preferably of not more than 3.0 wt.-%, like not more than 2.6 wt.-%, based on the total weight of the polypropylene matrix (M-HECO). Thus, a preferred range is 0.5 to 3.0 wt.-%, more preferred 0.5 to 2.5 wt.-%, based on the total weight of the propylene homopolymer (H-PP2).

In one embodiment of the present invention, the polypropylene matrix (M-HECO) is a propylene homopolymer (H-PP2) having a melt flow rate MFR₂ (230° C.) from 2.0 to 700 g/10 min, more preferably of from 4.0 to 400 g/10 min, still more preferably of from 15.0 to 200 g/10 min and most preferably of from 20.0 to 100 g/10 min.

If the polypropylene matrix (M-HECO) is a random propylene copolymer (RC-PP2), the random propylene copolymer (RC-PP2) preferably comprises, preferably consist of, units derived from

-   (i) propylene and -   (ii) ethylene and/or at least one C₄ to C₈ α-olefin, preferably at     least one α-olefin selected from the group consisting of ethylene,     1-butene, 1-pentene, 1-hexene and 1-octene, more preferably ethylene     and/or 1-butene, yet more preferably ethylene.

Accordingly, the random propylene copolymer (RC-PP2) may comprise units derived from (i) propylene and (ii) ethylene and/or at least one C₄ to C₈ α-olefin. In one embodiment of the present invention the random propylene copolymer (RC-PP2) comprises units derived from (i) propylene and (ii) an at least one α-olefin selected from the group consisting of ethylene 1-butene, 1-hexene and 1-octene. It is in particular preferred that the random propylene copolymer (RC-PP2) consists of units derived from propylene and ethylene. Preferably, the units derivable from propylene constitutes the main part of the random propylene copolymer (RC-PP2), i.e. at least 92 wt.-%, preferably of at least 95 wt.-%, more preferably of at least 98 wt.-%, still more preferably of 92 to 99.5 wt.-%, yet more preferably of 95 to 99.5 wt.-%, still more preferably of 98 to 99.2 wt.-%, based on the total weight of the random propylene copolymer (RC-PP2).

Furthermore, it is appreciated that the xylene cold soluble (XCS) content of the polypropylene matrix (M-HECO) being a random propylene copolymer (RC-PP2) is a rather low. Accordingly, the propylene copolymer (C-PP2) has preferably a xylene cold soluble (XCS) fraction measured according to ISO 6427 (23° C.) of not more than 14 wt-%, more preferably of not more than 13 wt.-%, yet more preferably of not more than 12 wt.-%, like not more than 11.5 wt.-%, based on the total weight of the propylene copolymer (C-PP2). Thus, a preferred range is 1 to 14 wt.-%, more preferred 1.0 to 13 wt.-%, still more preferred 1.2 to 11 wt.-%, based on the total weight of the propylene copolymer (C-PP2).

In one embodiment of the present invention, the random propylene copolymer (C-PP2) has a melt flow rate MFR₂ (230° C.) from 2.0 to 700 g/10 min, more preferably of from 4.0 to 400 g/10 min, still more preferably of from 15.0 to 200 g/10 min and most preferably of from 20.0 to 100 g/10 min.

The second component of the heterophasic propylene copolymer (HECO) is the elastomeric copolymer (E). As mentioned above the elastomeric copolymer (E) is preferably an elastomeric propylene copolymer (E1). In the following both elastomers are defined more precisely.

Preferably the elastomeric propylene copolymer (E1) comprises units derived from (i) propylene and (ii) ethylene and/or C₄ to C₂₀ α-olefins, preferably from (i) propylene and (ii) selected from the group consisting of ethylene, 1-butene, 1-hexene, and 1-octene. Preferably the propylene content in the elastomeric propylene copolymer (E1) is at least 40 wt.-%, more preferably at least 45 wt.-%. Thus in one preferred embodiment the elastomeric propylene copolymer (E1) comprises 40.0 to 85.0 wt.-%, more preferably 45.0 to 80 wt.-%, units derivable from propylene. The comonomers present in the elastomeric propylene copolymer (E1) are preferably ethylene and/or C₄ to C₂₀ α-olefins, like ethylene, 1-butene, 1-hexene and 1-octene. In one specific embodiment elastomeric propylene copolymer (E1) is a propylene-ethylene polymer. In one embodiment of the present invention, the elastomeric propylene copolymer (E1) is an ethylene propylene rubber (EPR1) with the amounts given in this paragraph.

Preferably the amount of the elastomeric copolymer (E), like the elastomeric propylene copolymer (E1), within the heterophasic propylene copolymer (HECO) ranges from 15 to 45 wt.-%, more preferably in the range of 20 to 40 wt.-%, like in the range of 25 to 35 wt.-%.

The intrinsic viscosity (IV) of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) is preferably moderate. Accordingly, it is appreciated that the intrinsic viscosity of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) is below 3.3 dl/g, more preferably below 3.1 dl/g, and most preferably below 3.0 dl/g. Even more preferred the intrinsic viscosity of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) is in the range of 1.5 to 3.3 dl/g, more preferably in the range 2.0 to 3.1 dl/g, still more preferably 2.2 to 3.0 dug.

It is especially preferred that heterophasic propylene copolymer (HECO) comprises a propylene homopolymer (H-PP2) as the polypropylene matrix (M-HECO) and an ethylene propylene rubber (EPR1) as the elastomeric propylene copolymer (E1).

Preferably, the heterophasic propylene copolymer (HECO) has a melt flow rate MFR₂ (230° C.) of not more than 100 g/10 min, more preferably in the range of 2 to 50 g/10 min, still more preferably in the range of 5.0 to 30 g/10 min, like in the range of 8.0 to 25 g/10 min.

Exceptional good results in terms of mechanical properties such as stiffness and impact are obtained if the instant fiber reinforced polymer composition comprises a propylene homopolymer (H-PP1) only as the polypropylene (PP).

Thus, it is preferred that the instant fiber reinforced polymer composition comprises a propylene homopolymer (H-PP1) as the polypropylene (PP)

The polypropylene (PP) may comprise a nucleating agent which is preferably a polymeric nucleating agent, more preferably an alpha-nucleating agent, e.g. a polymeric alpha-nucleating agent.

The (alpha)-nucleating agent content of the polypropylene (PP), or of one of its components, preferably of the polypropylene (PP), is preferably up to 5.0 wt.-%. In a preferred embodiment, the polypropylene (PP) or of one of its components, preferably of the polypropylene (PP), contains not more than 3000 ppm, more preferably of 1 to 2000 ppm of a (a)-nucleating agent, in particular selected from the group consisting of dibenzylidenesorbitol (e.g. 1,3:2,4 dibenzylidene sorbitol), dibenzylidenesorbitol derivative, preferably dimethyldibenzylidenesorbitol (e.g. 1,3:2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, vinylcycloalkane polymer, vinylalkane polymer, and mixtures thereof.

In a preferred embodiment the polypropylene (PP) or one of its components contains a vinylcycloalkane, like vinylcyclohexane (VCH), polymer and/or vinylalkane polymer, as the preferable alpha-nucleating agent. Preferably in this embodiment the polypropylene (PP) contains a vinylcycloalkane, like vinylcyclohexane (VCH), polymer and/or vinylalkane polymer, preferably vinylcyclohexane (VCH).

The nucleating agent can be introduced as a masterbatch. Alternatively some alpha-nucleating agents as defined in the present invention, can be also introduced by BNT-technology as described below.

The nucleating agent may be introduced to the polypropylene (PP) or one of its components e.g. during the polymerisation process of the polypropylene (PP) or one of its components or may be incorporated to the propylene copolymer in the form of masterbatch (MB) together with e.g. a carrier polymer.

In case of the embodiment of a masterbatch (MB) incorporation the masterbatch (MB) contains a nucleating agent, which is preferably a polymeric nucleating agent, more preferably alpha-nucleating agent, most preferably a vinylcycloalkane, like vinylcyclohexane (VCH), polymer and/or vinylalkane polymer, preferably vinylcyclohexane (VCH) polymer, as defined above or below, in an amount of not more than 500 ppm, more preferably of 1 to 200 ppm, and still more preferably of 5 to 100 ppm, based on the weight of the masterbatch (MB) (100 wt. %). In this embodiment, more preferably, said masterbatch (MB) is present in an amount of not more than 10.0 wt.-%, more preferably not more than 5.0 wt.-% and most preferably not more than 3.5 wt.-%, with the preferred amount of masterbatch (MB) being from 1.5 to 3.5 wt.-%, based on the total amount of the polypropylene (PP). Most preferably the masterbatch (MB) comprises, preferably consists of the homopolymer or copolymer, preferably homopolymer, of propylene which has been nucleated according to BNT-technology as described below.

It is preferred that the nucleating agent is introduced to the polypropylene (PP) during the polymerisation process of one of the components of the polypropylene (PP). The nucleating agent is preferably introduced to the polypropylene (PP) or one of its components by first polymerising the above defined vinyl compound, preferably vinylcycloalkane, as defined above or below, in the presence of a catalyst system comprising a solid catalyst component, preferably a solid Ziegler Natta catalyst component, a cocatalyst and optional external donor, and the obtained reaction mixture of the polymer of the vinyl compound, preferably vinyl cyclohexane (VCH) polymer, and the catalyst system is then used for producing the polypropylene (PP) or one of its components. The above incorporation of the polymeric nucleating agent to the polypropylene (PP) during the polymerization of said propylene copolymer is called herein as BNT-technology as described below.

Said obtained reaction mixture is herein below referred interchangeably as modified catalyst system.

Preferably the vinylcycloalkane is vinylcyclohexane (VCH) polymer which is introduced into the propylene copolymer by the BNT technology.

More preferably in this preferred embodiment, the amount of vinylcycloalkane, like vinylcyclohexane (VCH), polymer and/or vinylalkane polymer, more preferably of vinylcyclohexane (VCH) polymer, in the polypropylene (PP), or of one of its components, preferably of the polypropylene (PP), is not more than 500 ppm, more preferably of 1 to 200 ppm, most preferably 5 to 100 ppm.

With regard to the BNT-technology reference is made to the international applications WO 99/24478, WO 99/24479 and particularly WO 00/68315. According to this technology a catalyst system, preferably a Ziegler-Natta procatalyst, can be modified by polymerising a vinyl compound in the presence of the catalyst system, comprising in particular the special Ziegler-Natta procatalyst, an external donor and a cocatalyst, which vinyl compound has the formula:

CH₂═CH—CHR³R⁴

wherein R³ and R⁴ together form a 5- or 6-membered saturated, unsaturated or aromatic ring or independently represent an alkyl group comprising 1 to 4 carbon atoms, and the modified catalyst is used for the preparation of the polypropylene (PP) according to this invention. The polymerized vinyl compound acts as an alpha-nucleating agent. The weight ratio of vinyl compound to solid catalyst component in the modification step of the catalyst is preferably of up to 5 (5:1), preferably up to 3 (3:1) most preferably from 0.5 (1:2) to 2 (2:1). The most preferred vinyl compound is vinylcyclohexane (VCH).

The Carbon Fibers (CF)

It is appreciated that the fiber reinforced polymer composition shall have well-balanced mechanical properties such as high stiffness and high impact. In order to ensure a good stiffness, the fiber reinforced polymer composition comprises carbon fibers (CF). Thus, one essential component of the fiber reinforced polymer composition is the carbon fibers (CF).

The carbon fibers (CF) used in the fiber reinforced polymer composition have preferably an average length of from 0.5 to 300 mm, more preferably from 1.0 to 250 mm, for example 1.5 to 200 mm. More preferably, the carbon fibers (CF) used in the fiber reinforced polymer composition are preferably endless carbon fibers (CF). The carbon fibers preferably have an average diameter of from 2 to 30 μm, more preferably from 3 to 25 μm and most preferably from 5 to 20 μm.

Preferably, the carbon fibers (CF) have a density of from 1.3 to 2.2 g/cm³, more preferably from 1.4 to 2.1 g/cm³, most preferably from 1.5 to 1.9 g/cm³.

Preferably, the carbon fibers (CF) are in the form of a non-woven fabric.

Preferably, the non-woven fabric comprises at least 50 wt.-% carbon fibers (CF), more preferably at least 65 wt.-% carbon fibers, even more preferably at least 75 wt.-% carbon fibers (CF) and most preferably at least 80 wt.-%, based on the total weight of the non-woven fabric.

The non-woven fabric according to the invention may comprise polymeric compounds such as sizing agents and/or sewing threads.

It is appreciated that the non-woven fabric may be a recycled material which may contain additional compounds besides the preferred carbon fibers, e.g. sizing agents, glass fibers, sewing threads in a minor amount etc., depending on the intended first use.

In one embodiment, the non-woven fabric is free of polymeric materials. The carbon fibres are not considered to be polymeric materials.

If present, the amount of sewing thread is normally within the range of 0.25 to 10 wt. %, preferably within the range of 0.5 to 7.5 wt. % and most preferably within the range of 1.0 to 3.0 wt. % based on the total weight of the non-woven fabric. Suitable sewing threads are for example polyester fibres.

In one embodiment, the carbon fibers (CF), preferably the non-woven fabric, comprise a sizing agent in order to improve its wetting and coupling to the polymer matrix. Preferably, the carbon fibers (CF), preferably the non-woven fabric, comprise sizing agents on the surface of the fibers. Preferably, the carbon fibers (CF), preferably the non-woven fabric, comprise a sizing agent selected from epoxy resins, polyether-modified epoxy resins, polyurethane, amino-silane grafted polypropylene.

In one especially preferred embodiment, the carbon fibers (CF), preferably the non-woven fabric, comprise an epoxy-resin, more preferably a polyether-modified epoxy resin, as sizing agent. A suitable sizing agent is for example Duroxy SEF 968w distributed by Cytec. Film formers, lubricants, stabilizers and antistatic agents may also be comprised in the sizing agent.

Usually the amount of such sizing agent is 15 wt.-% or less, more preferably 10 wt.-% or less, and most preferably 7.5 wt.-% or less, based on the total weight of the carbon fibers (CF), preferably the non-woven fabric.

The non-woven fabric may be a recycled material which may contain these (and possibly also other) additional compounds besides the preferred carbon fibres.

In case the carbon fibers (CF) are in the form of a non-woven fabric, the non-woven fabric is preferably in the form of a stripe.

Usually the width of the stripe is not more than 300 mm. Preferably the stripe has a width of 10 to 300 mm, preferably a width of 25 to 250 mm and most preferably a width of 40 to 200 mm. Additionally or alternatively, the stripe preferably has a length of at least 50 cm, more preferably of at least 150 cm, and most preferably of at least 250 cm.

The stripe may be in the form of a reel. Thus, the length is not particularly limited. However, the length is is not particularly limited, i.e. the stripe may be a so-called “endless stripe”.

The average weight of the non-woven fabric is preferably within the range of 100 to 1000 g/m², more preferably within the range of 150 to 800 g/m² and most preferably within the range of 250 to 650 g/m².

The non-woven fabric is further characterised by a constant weight per area. Thus, the difference in weight between two sections of the non-woven fabric having an identical area expressed as the quotient of the section having the higher weight to the section having the lower weight is preferably within 10%, more preferably within 5%.

The preparation of non-woven fabric from carbon fibers (CF), e.g. rovings, or recycled material which may be in the form of a laid web, is well-known in the art. Suitable processes are, for example needle punching.

Preferably, the non-woven fabric is in the form of a non-woven fabric, preferably obtained by needle-punching

It is appreciated that the carbon fibers (CF) are preferably the only fibers present in the instant fiber reinforced polymer composition. Thus, the fiber reinforced polymer composition is preferably free of fibers (F) being selected from the group comprising glass fibers, metal fibers, mineral fibers, ceramic fibers and mixtures thereof. More preferably, the fiber reinforced polymer composition is free of fibers (F) other than the carbon fibers (CF).

In one embodiment, the fiber reinforced polymer composition is free of fibers (F) having an average diameter of more than 15 μm, preferably of more than 12 μm and most preferably of more than 9 μm. Additionally or alternatively, the fiber reinforced polymer composition is free of fibers (F) having an average diameter of less than 2 μm, preferably of less than 3 μm and most preferably of less than 5 μm.

The Polar Modified Polypropylene (PMP) as Coupling Agent

In order to achieve an easier and more uniform dispersion of the carbon fibers (CF) in the polymer components which act in the fiber reinforced polymer composition as a matrix, the fiber reinforced polymer composition comprises a specific coupling agent.

The coupling agent according to this invention is a specific polar modified polypropylene (PMP).

The polar modified polypropylene (PMP) preferably is a polypropylene containing polar groups. In the following the polypropylene will be defined more precisely which is subsequently modified to the polar modified polypropylene (PMP) as explained in detail below.

The polypropylene is preferably a propylene homopolymer or a random propylene copolymer, like a copolymer of (i) propylene and (ii) ethylene and/or C₄ to C₁₂ α-olefins, preferably from (i) propylene and (ii) an α-olefin selected from the group consisting of ethylene, 1-butene, 1-hexene, and 1-octene. Concerning the definition of“random” reference is made to the information provided above.

In one embodiment, the polar modified polypropylene (PMP) is a modified random propylene copolymer, wherein said random propylene copolymer comprises ethylene as the only comonomer unit.

Preferably, the units derivable from propylene constitutes the main part of the random propylene copolymer, i.e. at least 90.0 wt.-%, more preferably in the range of 92.0 to 99.5 wt.-%, yet more preferably of 92.5 to 98.0 wt.-%, even more preferably of 93.0 to 96.0 wt.-%, based on the total weight of the propylene copolymer. Accordingly, the amount of units derived from ethylene and/or C₄ to C₁₂ α-olefins, preferably derived from ethylene, in the random propylene copolymer is at most 10.0 wt.-%, more preferably in the range of 0.5 to 8.0 wt.-%, yet more preferably of 2.0 to 7.5 wt.-%, even more preferably of 4.0 to 7.0 wt.-%, based on the total weight of the random propylene copolymer. It is in particular appreciated that the random propylene copolymer only comprises units derivable from propylene and ethylene. The comonomer amounts given in this paragraph belong preferably to the random propylene copolymer which is not modified.

Additionally, it is appreciated that the random propylene copolymer has a melting temperature T_(m) in the range of 125 to 140° C., more preferably ranges from 128 to 138° C. and most preferably ranges from 131 to 136° C. The melting temperature given in this paragraph is the melting temperature of the non-modified random propylene copolymer.

Additionally or alternatively, the random propylene copolymer, i.e. the non-modified random propylene copolymer, has a melt flow rate MFR₂ (230° C.) measured according to ISO 1133 in the range from 1 to 30 g/10 min, preferably in the range of 1 to 20 g/10 min, more preferably in the range of 1 to 10 g/10 min, and most preferably in the range of 2 to 6 g/10 min.

It is appreciated that the polar modified polypropylene (PMP) comprises groups derived from polar groups. In this context, preference is given to polar modified polypropylene (PMP) comprising groups derived from polar compounds, in particular selected from the group consisting of acid anhydrides, carboxylic acids, carboxylic acid derivatives, primary and secondary amines, hydroxyl compounds, oxazoline and epoxides, and also ionic compounds.

Specific examples of the said polar groups are unsaturated cyclic anhydrides and their aliphatic diesters, and the diacid derivatives. In particular, one can use maleic anhydride and compounds selected from C₁ to C₁₀ linear and branched dialkyl maleates, C₁ to C₁₀ linear and branched dialkyl fumarates, itaconic anhydride, C₁ to C₁₀ linear and branched itaconic acid dialkyl esters, maleic acid, fumaric acid, itaconic acid and mixtures thereof.

In terms of structure, the polar modified polypropylene (PMP) is preferably selected from graft or block copolymers preferably of the above defined polypropylene, like the above defined random propylene copolymer.

Preferably the polar modified polypropylene (PMP), i.e. the coupling agent, is a polypropylene, like the random propylene copolymer as defined above in the section “the polar modified propylene (PMP) as coupling agent”, grafted with such polar group.

Particular preference is given to using a polypropylene, like the random propylene copolymer as defined above in the section “the polar modified propylene (PMP) as coupling agent”, grafted with maleic anhydride as the polar modified polypropylene (PMP), i.e. the coupling agent.

In one embodiment, the polar modified polypropylene (PMP) is a random propylene copolymer as defined above grafted with maleic anhydride. Thus in one specific preferred embodiment the polar modified polypropylene (PMP) is a random propylene ethylene copolymer grafted with maleic anhydride, more preferably wherein the ethylene content based on the total amount of the random propylene ethylene copolymer is in the range of 2.0 to 7.5 wt.-%, more preferably in the range of 4.0 to 7.0 wt.-%.

In order to achieve the desired dispersion of the carbon fibers (CF) in the polymer components ensuring that the fiber reinforced polymer composition provides the well-balanced mechanical properties such as high stiffness and impact at low density, it is appreciated that the polar modified polypropylene (PMP) comprises an amount of groups deriving from polar groups which is higher than that typically used in polar modified polypropylenes considered for polypropylenes.

Required amounts of groups deriving from polar groups in the polar modified polypropylene (PMP) are thus from 0.5 to 5.0 wt.-%, based on the total weight of the polar modified polypropylene (PMP). Preferably, the amount of groups deriving from polar groups in the polar modified polypropylene (PMP) are from 1.5 to 4.0 wt.-%, more preferably from 2.0 to 3.0 wt.-%, most preferably from 2.0 to 2.8 wt.-%, such as from 2.2 to 2.4 wt.-%, based on the total weight of the polar modified polypropylene (PMP).

Thus in one specific preferred embodiment the polar modified polypropylene (PMP) is a random propylene ethylene copolymer grafted with maleic anhydride, more preferably wherein the ethylene content based on the total amount of the random propylene ethylene copolymer is in the range of 2.0 to 7.5 wt.-%, more preferably in the range of 4.0 to 7.0 wt.-% and/or the amount of groups deriving from the maleic anhydride in the polar modified polypropylene (PMP) is from 1.5 to 4.0 wt.-%, more preferably from 2.0 to 3.0 wt.-%, most preferably from 2.0 to 2.8 wt.-%, such as from 2.2 to 2.4 wt.-%, based on the total weight of the polar modified polypropylene (PMP).

Preferred values of the melt flow index MFI (170° C.; 1.2 kg) measured in line with the general definitions of ISO 1133 for the polar modified polypropylene (PMP) are from 10 to 150 g/10 min, like in the range of 30 to 120 g/10 min. For example, the polar modified polypropylene (PMP) has a melt flow index MFI (170° C.; 1.2 kg) measured in line with the general definitions of ISO 1133 from 50 to 100 g/10 min, of from 60 to 80 g/10 min.

Preferred values of the melt flow rate MFR₂ (230° C.; 2.16 kg) for the polar modified polypropylene (PMP) are from 350 to 600 g/10 min, like in the range of 400 to 550 g/10 min. Additionally or alternatively, it is appreciated that the polar modified polypropylene (PMP) preferably has a melting temperature T_(m) in the range of 120 to 150° C., more preferably ranges from 125 to 145° C. and most preferably ranges from 130 to 140° C.

The polar modified polypropylene (PMP) can be produced in a simple manner by a two-step grafting process comprising a solid stage as a first step and a melt stage as a second step. Such process steps are well known in the art.

The polar modified polypropylene (PMP) is known in the art and commercially available. A suitable example is SCONA TSPP 3598 GB of BYK.

In one embodiment, the fiber reinforced polymer composition comprises the polar modified polypropylene (PMP) as defined above as the only polar modified polypropylene (PMP).

Optional Components

The term “additive” covers also additives which are provided as a masterbatch containing the polymeric carrier material as discussed above. However the term “additive” does not cover nucleating agents, e.g. α-nucleating agents. Typical additives are acid scavengers, antioxidants such as phenolic antioxidant (AO) and the hindered amine light stabilizer (HALS), colorants, pigments such as talc, anti-scratch agents, dispersing agents and carriers.

The term “at least one” additive in the meaning of the present invention means that the additive comprises, preferably consists of, one or more additive(s).

In one embodiment of the present invention, the at least one additive comprises, preferably consists of, one additive. Alternatively, the at least one additive comprises, preferably consists of, a mixture of two or more additives. For example, the at least one earth alkali hydrogen carbonate comprises, preferably consists of, of a mixture of two or three additives.

Preferably, the at least one additive comprises, more preferably consists of, a mixture of two or more additives.

In one embodiment, the fiber reinforced polymer composition comprises talc and optionally further additives. If the fiber reinforced polymer composition comprises talc, talc is preferably present in an amount from 0.1 to 2 wt.-%, more preferably from 0.1 to 0.5 wt.-% and most preferably from 0.3 to 0.5 wt.-%, based on the total weight of the fiber reinforced polymer composition. The talc preferably has a particle size typically used in this area. For example, the talc has a median particle size d₅₀ in the range from 0.1 to 5 μm, preferably from 0.5 to 4.5 μm, more preferably from 1 to 4 μm and most preferably from 1.5 to 3.5 μm. Additionally or alternatively, the talc has a particle size d₉₉ in the range from 5 to 25 μm, preferably from 8 to 20 μm, more preferably from 9 to 18 μm and most preferably from 10 to 15 μm. Such talc as additive in polymer compositions is available from a great variety of sources, for example, from IMI-Fabi, Italy.

In the meaning of the present invention, the particle size is specified as weight median particle size d₅₀ unless indicated otherwise. The d₅₀ value is thus the weight median particle size, i.e. 50 wt.-% of all grains are bigger and the remaining 50 wt.-% of grains smaller than this particle size. For determining the weight median particle size d₅₀ value a Sedigraph, i.e. the sedimentation method, can be used.

In addition, the fiber reinforced polymer composition contains preferably a α-nucleating agent. Even more preferred the present fiber reinforced polymer composition is free of β-nucleating agents. Accordingly, the nucleating agent is preferably selected from the group consisting of

-   (i) salts of monocarboxylic acids and polycarboxylic acids, e.g.     sodium benzoate or aluminum tert-butylbenzoate, and -   (ii) dibenzylidenesorbitol (e.g. 1,3:2,4 dibenzylidenesorbitol) and     C₁-C₈-alkyl-substituted dibenzylidenesorbitol derivatives, such as     methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or     dimethyldibenzylidenesorbitol (e.g. 1,3:2,4 di(methylbenzylidene)     sorbitol), or substituted nonitol-derivatives, such as     1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol,     and -   (iii) salts of diesters of phosphoric acid, e.g. sodium     2,2′-methylenebis (4, 6,-di-tert-butylphenyl) phosphate or     aluminium-hydroxy-bis[2,2′-methylene-bis(4,6-di-t-butylphenyl)phosphate],     and -   (iv) vinylcycloalkane polymer and vinylalkane polymer, and -   (v) mixtures thereof.

Preferably the fiber reinforced polymer composition contains as α-nucleating agent a vinylcycloalkane polymer and/or a vinylalkane polymer.

Such additives and nucleating agents are generally commercially available and are described, for example, in “Plastic Additives Handbook”, 5th edition, 2001 of Hans Zweifel.

The fiber reinforced polymer composition according to the present invention optionally comprises an elastomeric copolymer (ECP).

It is appreciated that the elastomeric copolymer (ECP) is preferably present in the fiber reinforced polymer composition in case the fiber reinforced polymer composition comprises the polypropylene (PP) in an amount of below 70 wt.-%, based on the total weight of the fiber reinforced polymer composition.

For example, the elastomeric copolymer (ECP) is present in the fiber reinforced polymer composition in case the fiber reinforced polymer composition comprises the polypropylene (PP) in an amount ranging from 39 to 70 wt.-%, more preferably from 45 to 70 wt.-%, most preferably from 55 to 70 wt.-%, like from 60 to 70 wt.-%, based on the total weight of the fiber reinforced polymer composition.

In case the fiber reinforced polymer composition comprises elastomeric copolymer (ECP), the elastomeric copolymer (ECP) is preferably present in an amount ranging from 2.0 to 15.0 wt.-%, more preferably from 5.0 to 12.5 wt.-% and most preferably from 7.5 to 12.5 wt.-%, based on the total weight of the fiber reinforced polymer composition.

The elastomeric copolymer (ECP) preferably has a melt flow rate MFR₂ (190° C.; 2.16 kg) measured according to ISO 1133 in the range of 0.25 to 45.0 g/10 min, preferably in the range of 0.25 to 30.0 g/10 min and most preferably in the range of 0.25 to 10.0 g/10 min.

The elastomeric copolymer (ECP) typically has a density of equal or less than 0.935 g/cm³, preferably of equal or less than 0.920 g/cm³, more preferably of equal or less than 0.910 g/cm³, still more preferably in the range of 0.850 to 0.910 g/cm³, like in the range of 0.850 to 0.905 g/cm³.

It is preferred that the elastomeric copolymer (ECP) is an ethylene copolymer with comonomers selected from C₄ to C₈ α-olefins. For example, the elastomeric copolymer (ECP) comprises especially consists of, monomers copolymerizable with ethylene from the group consisting of propylene, 1-butene, 1-hexene and 1-octene.

More specifically, the elastomeric copolymer (ECP) comprises—apart from ethylene—units derivable from 1-hexene and 1-octene. In a preferred embodiment the elastomeric copolymer (ECP) comprises units derivable from ethylene and 1-octene only.

Additionally, it is appreciated that the elastomeric copolymer (ECP) has preferably a comonomer content in the range from 15.0 to 55.0 wt.-%, more preferably in the range from 25.0 to 40.0 wt.-%, based on the total weight of the elastomeric copolymer (ECP).

It is appreciated that the fiber reinforced polymer composition comprises the elastomeric copolymer (ECP) in that it is dispersed in the polypropylene (PP).

It is preferred that the elastomeric copolymer (ECP) is present in a specific weight ratio compared to the polypropylene (PP) and/or the carbon fibers (CF) in the fiber reinforced polymer composition.

For example, the weight ratio of polypropylene copolymer (PP) to the elastomeric copolymer (ECP) [PP/ECP] is at least 3. Preferably, the weight ratio of polypropylene (PP) to the elastomeric copolymer (ECP) [PP/ECP] is from 20:1 to 3:1, more preferably from 15:1 to 4:1, and most preferably from 10:1 to 5:1.

Additionally or alternatively, the weight ratio of the carbon fibers (CF) to the elastomeric copolymer (ECP) [CF/ECP] is below 8. Preferably, the weight ratio of the carbon fibers (CF) to the elastomeric copolymer (ECP) [CF/ECP] is from 8:1 to 1:1, more preferably from 5:1 to 1:1, and most preferably from 3:1 to 1:1.

The Article

The invention is also directed to an article comprising the fiber reinforced polymer composition according to this invention. Preferably the article comprises at least 80 wt.-%, like 80 to 99.9 wt.-%, more preferably at least 90 wt.-%, like 90 to 99.9 wt.-%, yet more preferably at least 95 wt.-%, like 95 to 99.9 wt.-%, of the fiber reinforced polymer composition according to this invention. In one embodiment the article consists of the fiber reinforced polymer composition according to this invention.

Preferably, the article is a molded article, preferably an injection molded article or a foamed article.

The article can be a part of washing machines or dishwashers or automotive articles, especially of car interiors and exteriors.

Preferred automotive articles are selected from the group consisting of instrumental carriers, shrouds, structural carriers, bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like.

Automotive articles are typically molded articles, preferably injection molded articles as well as foamed articles. Preferably the automotive articles, especially those defined in the previous paragraph are injection molded articles.

The fiber reinforced polymer composition of the present invention can be also used for the production of articles, preferably molded articles, more preferably injection molded articles as well as foamed articles.

In a further aspect, the present invention also refers to the use of the fiber reinforced polymer composition of the present invention for the production of articles, such as parts of washing machines or dishwashers as well as automotive articles, especially of car interiors and exteriors, like instrumental carriers, shrouds, structural carriers, bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like.

In the following the invention is described in more detail.

EXAMPLES 1. Definitions/Measuring Methods

The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

Quantification of Microstructure by NMR Spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy is used to quantify the isotacticity and regio-regularity of the polypropylene homopolymers.

Quantitative ¹³C{¹H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for ¹H and ¹³C respectively. All spectra were recorded using a ¹³C optimised 10 mm extended temperature probehead at 125° C. using nitrogen gas for all pneumatics.

For polypropylene homopolymers approximately 200 mg of material was dissolved in 1,2-tetrachloroethane-d₂ (TCE-d₂). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatary oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution needed for tacticity distribution quantification (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V.; Cipullo, R., Monaco, G., Vacatello, M., Segre, A. L., Macromolecules 30 (1997) 6251). Standard single-pulse excitation was employed utilising the NOE and bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 11289). A total of 8192 (8 k) transients were acquired per spectra.

Quantitative ¹³C{¹H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs.

For polypropylene homopolymers all chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

Characteristic signals corresponding to regio defects (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N., Macromolecules 17 (1984), 1950) or comonomer were observed.

The tacticity distribution was quantified through integration of the methyl region between 23.6-19.7 ppm correcting for any sites not related to the stereo sequences of interest (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A. L., Macromolecules 30 (1997) 6251).

Specifically the influence of regio-defects and comonomer on the quantification of the tacticity distribution was corrected for by subtraction of representative regio-defect and comonomer integrals from the specific integral regions of the stereo sequences.

The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences:

[mmmm]%=100*(mmmm/sum of all pentads)

The presence of 2,1 erythro regio-defects was indicated by the presence of the two methyl sites at 17.7 and 17.2 ppm and confirmed by other characteristic sites. Characteristic signals corresponding to other types of regio-defects were not observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

The amount of 2,1 erythro regio-defects was quantified using the average integral of the two characteristic methyl sites at 17.7 and 17.2 ppm:

P_(21e)=(I_(e6)+I_(e8))/2

The amount of 1,2 primary inserted propene was quantified based on the methyl region with correction undertaken for sites included in this region not related to primary insertion and for primary insertion sites excluded from this region:

P₁₂=I_(CH3)+P_(12e)

The total amount of propene was quantified as the sum of primary inserted propene and all other present regio-defects:

P_(total)=P₁₂+P_(21e)

The mole percent of 2,1-erythro regio-defects was quantified with respect to all propene:

[21e]mol.-%=100*(P_(21e)/P_(total))

Characteristic signals corresponding to the incorporation of ethylene were observed (as described in Cheng, H. N., Macromolecules 1984, 17, 1950) and the comonomer fraction calculated as the fraction of ethylene in the polymer with respect to all monomer in the polymer.

The comonomer fraction was quantified using the method of W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157, through integration of multiple signals across the whole spectral region in the ¹³C{¹H} spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

The mole percent comonomer incorporation was calculated from the mole fraction.

The weight percent comonomer incorporation was calculated from the mole fraction.

MFR₂ (230° C.) is measured according to ISO 1133 (230° C., 2.16 kg load).

MFR₂ (190° C.) is measured according to ISO 1133 (190° C., 2.16 kg load).

MFR (170° C.) is measured in line with the general definitions of ISO 1133 (170° C., 1.2 kg load).

DSC analysis, melting temperature (Tm) and melting enthalpy (Hm), crystallization temperature (Tc) and crystallization enthalpy (Hc): measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 11357/part 3/method C2 in a heat/cool/heat cycle with a scan rate of 10° C./min in the temperature range of −30 to +225° C. Crystallization temperature and crystallization enthalpy (Hc) are determined from the cooling step, while melting temperature and melting enthalpy (Hm) are determined from the second heating step.

The glass transition temperature Tg is determined by dynamic mechanical analysis according to ISO 6721-7. The measurements are done in torsion mode on compression moulded samples (40×10×1 mm³) between −100° C. and +150° C. with a heating rate of 2° C./min and a frequency of 1 Hz.

Density of the polymer composition is measured according to ISO 1183-187. Sample preparation is done by compression molding in accordance with ISO 1872-2:2007.

The xylene cold solubles (XCS, wt.-%): Content of xylene cold solubles (XCS) is determined at 25° C. according to ISO 16152; first edition; Jul. 1, 2005

Intrinsic viscosity is measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135° C.).

Tensile Modulus; Tensile strength are measured according to ISO 527-2 (cross head speed=1 mm/min; 23° C.) using injection molded specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness).

Charpy notched impact strength is determined according to ISO 179 1eA at 23° C. by using an 80×10×4 mm³ test bars injection molded in line with EN ISO 1873-2.

Average fiber diameter is determined according to ISO 1888:2006(E), Method B, microscope magnification of 1000.

2. Examples

The following inventive example IE1 and comparative examples CE1 and CE2 were prepared by compounding on a co-rotating twin-screw extruder (ZSK 40 from Coperion).

The following process parameters were used:

-   -   throughput of 100 kg/h     -   screw speed of 100-150 rpm     -   barrel temperatures of 250° C. flat     -   die plate with 5 mm holes, whereby 3 holes were opened.

The polymer and the components different from the carbon fibers were fed to the extruder and melt-kneaded in the 4^(th) barrel of the extruder which consists of three kneading blocks (two times a KB 45/5/40, followed by a KB 45/5/20 LH) and a left-handed conveying element. The carbon fibers were added in the 6^(th) barrel using a side feeder. A second kneading zone located in the 8^(th) barrel and consisting of three kneading blocks (KB 45/5/20) was used to distribute the carbon fibers homogeneously. Moreover, two TME elements (one TME 22.5/20 and one TME 22.5/20 LH) located between the 8^(th) and the 9^(th) barrel were used to further distribute the carbon fibers.

Table 1 summarizes the composition of the inventive and comparative examples and their properties

TABLE 1 Overview of composition and mechanics for inventive and comparative examples IE 1* CE 1* CE 2* PP [wt.-%] 63.35 63.35 PP-1 [wt.-%] 64 Carbon fibers [wt.-%] 20 20 Glass fibers [wt.-%] 22 Carbon black [wt.-%] 0.5 ECP1 [wt.-%] 10 10 ECP2 [wt.-%] 10 PMP [wt.-%] 5 PMP2 [wt.-%] 5 PMP2a [wt.-%] 1.5 MFR2 (230° C./2.16 kg) [g/10 min] 10.64 4.76 2 Density [g/cm³] 1084 1084 1232 Tensile modulus [MPa] 10835 11455 5300 Tensile strength [MPa] 110.7 97.6 105 Charpy impact strength [kJ/m²] 37.33 21.51 57 unnotched +23° C. *remaining part up 100 wt.-% are typical additives like antioxidants, carrier etc.

“PP” is the commercial propylene homopolymer HF955MO of Borealis AG having a melt flow rate MFR2 (230° C.) of 19.5 g/10 min and a melting temperature of 167° C.;

“PP-1” is the commercial propylene homopolymer HK060AE of Borealis AG having a melt flow rate MFR2 (230° C.) of 125 g/10 min and a melting temperature of 165° C.;

“Carbon fiber” is a non-woven fabric comprising 80 wt.-% of carbon fibers and has been produced by needle-punching: The carbon fibers have an average diameter of 7 μm.

“Glass fibers” is a glass fiber having an average diameter of 17 μm and is an endless roving before production, about 10 mm length after pelletizing;

“ECP1” is the commercial product Engage 8100 of Dow Elastomers (USA), which is an ethylene-1-octene copolymer having a density of 0.870 g/cm³, a melt flow rate MFR₂ (190° C.) of 1.0 g/10 min and a 1-octene content of 25 wt.-%;

“ECP2” is the commercial product Queo 8230 of Borealis Plastomers, which is an ethylene-1-octene copolymer having a density of 0.882 g/cm³, a melt flow rate MFR₂ (190° C.) of 30 g/10 min and a 1-octene content of 17 wt.-%;

“PMP” is the ethylene polypropylene copolymer (functionalized with maleic anhydride)

“TSPP3598 GB” of BYK Co. Ltd, Germany, having a MFI (170° C.) of 71 g/10 min and a maleic anhydride content of 2.2-2.4 wt.-% wherein further the ethylene polypropylene copolymer has an ethylene content of 5.6 wt.-%;

“PMP2” is the polypropylene (functionalized with maleic anhydride) “TPPP8112 FA” of BYK Co. Ltd, Germany, having a MFR₂ (190° C.; 2.16 kg) of more than 80 g/10 min and a maleic anhydride content of 1.4 wt.-%;

“PMP2a” is the polypropylene (functionalized with maleic anhydride) “TPPP9012 GA” of BYK Co. Ltd, Germany, having a MFR₂ (190° C.; 2.16 kg) of 50-110 g/10 min and a maleic anhydride content of more than 0.9%.

It can be gathered from table 1 that the inventive example IE1 comprising carbon fibers in combination with a specific polar modified polypropylene in a polypropylene matrix has well-balanced mechanical properties such as stiffness and impact, at reduced density. Moreover, compared to the comparative examples CE1 and CE2, using a polar modified polypropylene (PMP) that is typically used as coupling agents in polypropylenes, a significant improvement in the impact related properties is obtained, but keeping a comparable modulus value. 

1: A fiber reinforced polymer composition comprising: (a) from 39 to 94 wt. %, based on the total weight of the fiber reinforced polymer composition, of a polypropylene (PP); (b) from 5 to 60 wt. %, based on the total weight of the fiber reinforced polymer composition, of carbon fibers (CF); and (c) from 1 to 10 wt. %, based on the total weight of the fiber reinforced polymer composition, of a polar modified polypropylene (PMP) as coupling agent, wherein the polar modified polypropylene (PMP) comprises groups derived from polar groups in an amount of from 1 to 5 wt. %, based on the total weight of the polar modified polypropylene (PMP), wherein the carbon fibers (CF) are in the form of a non-woven fabric. 2: The fiber reinforced polymer composition according to claim 1, wherein the polypropylene (PP) has: (a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to ISO 1133 of not more than 100 g/10 min; and/or (b) a melting temperature T_(m) in the range of 160 to 170° C.; and/or (c) a ratio of weight average molecular weight (M_(w)) to number average molecular weight (M_(n)) [M_(w)/M_(n)] of from 1 to
 10. 3: The fiber reinforced polymer composition according to claim 1, wherein the polypropylene (PP) is a propylene homopolymer (H-PP1) and/or a propylene copolymer (C-PP1). 4: The fiber reinforced polymer composition according to claim 1, wherein the non-woven fabric comprises at least 50 wt. % carbon fibers (CF), based on the total weight of the non-woven fabric. 5: The fiber reinforced polymer composition according to claim 1, wherein the carbon fibers (CF) comprise a sizing agent. 6: The fiber reinforced polymer composition according to claim 1, wherein the fiber reinforced polymer composition is free of fibers (F) being selected from the group comprising glass fibers, metal fibers, mineral fibers, ceramic fibers and mixtures thereof. 7: The fiber reinforced polymer composition according to claim 1, wherein the polar modified polypropylene (PMP) comprises groups derived from polar groups selected from the group consisting of acid anhydrides, carboxylic acids, carboxylic acid derivatives, primary and secondary amines, hydroxyl compounds, oxazoline and epoxides, and also ionic compounds. 8: The fiber reinforced polymer composition according to claim 1, wherein the polar modified polypropylene (PMP) is a propylene polymer grafted with maleic anhydride. 9: The fiber reinforced polymer composition according to claim 8, wherein the polar modified polypropylene (PMP) is a propylene copolymer grafted with maleic anhydride. 10: The fiber reinforced polymer composition according to claim 1, wherein the fiber reinforced polymer composition further comprises at least one additive in an amount of up to 20 wt. %, based on the total weight of the fiber reinforced polymer composition. 11: The fiber reinforced polymer composition according to claim 1, wherein the fiber reinforced polymer composition further comprises 2.0 to 15.0 wt. %, based on the total weight of the fiber reinforced polymer composition, of an elastomeric copolymer (ECP) comprising units derived from ethylene and C₄ to C₈ α-olefins. 12: The fiber reinforced polymer composition according to claim 1, wherein the fiber reinforced polymer composition has: (a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according to ISO 1133 of from 5 to 75 g/10 min; and/or (b) density of equal or less than 1.200 g/cm³; and/or (c) a Charpy notched impact strength at +23° C. of ≥5.5 kJ/m²; and/or (d) a tensile strength according to ISO 527-2 of at least 100 MPa. 13: An article comprising a fiber reinforced polymer composition according to claim
 1. 14: The article according to claim 13, wherein the article is a molded article. 15: The article according to claim 13, wherein the article is a part of washing machines or dishwashers or automotive articles, especially of car interiors and exteriors, like instrumental carriers, shrouds, structural carriers, bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like. 